Duncan is an old US brand mostly active in the past century…
Between others, they notably always tried to push spintops on the stage, regarding that, they for example, recorded many videos about learning yoyos and spintops
One master piece is still the VHS “How to be a player” here is an archived version of the second volume dedicated to spintops:
You can still find some of their tops on the market especially the RipCord and the Bearing King:
